1. Field of the Invention
This invention generally relates to a damper mechanism. More specifically, the present invention relates to a damper mechanism for transmitting a torque while absorbing and damping torsional vibrations.
2. Background Information
A damper mechanism used in a clutch disk assembly of a vehicle has, e.g., an input rotary member, an output rotary member, and an elastic coupling mechanism. The input rotary member is releasably coupled to an input flywheel. The output rotary member is coupled to an input shaft of a transmission. The elastic coupling mechanism elastically couples the rotary members in a rotating direction. The input rotary member is formed of a clutch disk and a pair of input plates fixed to the clutch disk. The output rotary member is formed of a hub, which is unrotatably and axially movably coupled to the transmission input shaft. The hub is formed of a cylindrical boss and a radial flange. The cylindrical boss is spline-engaged with the transmission input shaft, and the radial flange is formed around the boss. The elastic coupling mechanism is formed of a plurality of elastic member assemblies. Each elastic member assembly is formed of a single coil spring or a combination of the coil spring and seat members arranged on opposite ends of the coil spring. Each elastic member assembly is arranged in a window aperture formed in the flange, and is supported at its opposite ends in the rotating direction. Each elastic member assembly is supported in various directions by edges of windows formed in the input plate pair.
In the structure described above, when the input plate pair rotates relatively to the hub, the coil springs are compressed in the rotating direction between the input plates and the hub. Thereby, torsional vibrations supplied to the clutch disk assembly are absorbed and damped by the damper mechanism.
In general, noises generated from a drive system due to torsional vibrations can be classified into groups, each including noises during idling, noises during constant-speed driving, noises during acceleration and deceleration, and muffled or confined noises. For absorbing the torsional vibrations, which may cause these noises, it is therefore necessary to determine the appropriate torsion characteristics for the damper mechanism. Therefore, some conventional damper mechanisms have employed two-stage characteristics. A conventional two-stage damper mechanism achieves a low rigidity and a low hysteresis torque in a region of a small torsion angle for absorbing vibrations during idling. In these conventional two-stage characteristics, the region of high torsion angles may be divided into a region exhibiting an intermediate rigidity and a high hysteresis torque for absorbing muffled noises, as well as a region exhibiting a high rigidity and a high hysteresis torque for absorbing vibrations and noises during acceleration.
In an FF (Front-engine and Front-drive) vehicle, a drive system has a high rigidity so that a resonance point remains in a practical operation range even if the torsion rigidity is reduced for the purpose of improving performance relating to suppression of noises and vibrations. Characteristics of engine speed variations are different between the positive or acceleration side and the negative or deceleration side. In a conventional structure, however, no difference is present in the torsion characteristics between the positive and negative sides. Therefore, even if good damping characteristics can be realized on one side, good damping characteristics cannot be realized on the other side. Thus, good damping characteristics cannot be realized on both the sides.
In connection with the vibration damping performance relating to variations in rotation speed of the transmission with respect to the engine rotation speed, the hysteresis torque can suppress resonance on the positive side, but cannot achieve an adequate damping rate in a positive range lower than the resonance point and the whole negative range. Conversely, the low hysteresis torque can achieve adequate damping rates in the positive range lower than the resonance point and the whole negative range, but cause large variations in rotation speed at the positive resonance point. If the torsion characteristics on the positive side are similar to those on the negative side, and particularly if no difference is present in hysteresis torque between the positive and negative sides, it is impossible to provide torsional damping characteristics that are preferable over the whole operating range of the damper mechanism.
A structure in which the number of elastic members operating on the positive side is larger than the number of elastic members operating on the negative side is known. This structure can thereby provide a rigidity on the positive side that is different from a rigidity on the negative side. Additionally, a structure in which friction generated on the positive side by a friction generating mechanism is different in magnitude from that on the negative side is known as well. However, the friction generating mechanism requires a plurality of friction washers and conical springs, and thus requires a complicated structure formed of a large number of parts.
In view of the above, there exists a need for damper mechanism that which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the invention is to provide a damper mechanism with a simplified structure that can achieve the preferable vibration damping characteristics by providing different torsion characteristics on the positive and negative sides.
According to a first aspect of the present invention, a damper mechanism includes a first rotary member, a second rotary member, a first elastic member, a second elastic member, and a friction generating mechanism. The second rotary member is rotatable with respect to the first rotary member. The first elastic member couples the first and second rotary members together in a rotating direction. The first elastic member is compressed in the rotating direction when relative rotation occurs between the first and second rotary members, and is compressed on positive and negative sides of torsion characteristics. The second elastic member couples the first and second rotary members together in the rotating direction. The second elastic member is compressed in the rotating direction when relative rotation occurs between the first and second rotary members, and is arranged to operate in parallel in the rotating direction with respect to the first elastic member. The second elastic member is compressed on the positive side of the torsion characteristics, and is compressed on the negative side of the torsion characteristics only in a range exceeding a predetermined torsion angle. The friction generating mechanism generates a friction resistance only when the second elastic member is compressed in the rotating direction.
According to the damper mechanism described above, when the first and second rotary members rotate relatively to each other, the first and second elastic members are compressed therebetween to provide predetermined torsion characteristics. On the positive side of the torsion characteristics, the first and second elastic members are compressed to provide a predetermined rigidity. Further, the friction generating mechanism generates friction in accordance with compression of the second elastic member. On the negative side of the torsion characteristics, only the first elastic member is compressed before the torsion angle exceeds a predetermined value. Thus, the second elastic member is not compressed, and the friction generating mechanism does not generate friction. Owing to the above operations, such characteristics can be achieved on the negative side that rigidity is low, and friction is not generated by the friction generating mechanism.
In summary, this damper mechanism can provide characteristics in which a predetermined rigidity and hysteresis torque are produced on the positive side acceleration side of the torsion characteristics, and low rigidity and extremely low hysteresis torque are produced on the negative side or deceleration side of the torsion characteristics. As a result, it is possible to suppress variations in rotation speed, which may occur when passing through the resonance point, on the positive side of the torsion characteristics. Also, good damping rates can be realized throughout the negative side of the torsion characteristics. In particular, the resonance point can be lowered to a range of small variations in engine speed because the characteristics of a low rigidity on the deceleration side can be achieved by not compressing the second elastic member. Therefore, variations in engine speed do not increase even when resonance occurs. Accordingly, it is possible to eliminate a friction generating portion that operates on the deceleration side. Thus, the damper mechanism can be structured to have a simplified structure with regards to the member of parts.
According to a second aspect of the present invention, a damper mechanism includes a first rotary member, a second rotary member, a first elastic member, a second elastic member, and a friction generating mechanism. The first rotary member is formed of a pair of circular plate members aligned in an axial direction and provided with a plurality of spring support portions. The second rotary member has a plate portion arranged between the pair of circular plate members and provided with a plurality of spring accommodating apertures, and is directly and axially contactable with the paired circular plate members. The first elastic member is arranged in the spring support portion and the spring accommodating aperture. The first elastic member is compressed on the positive and negative sides of torsion characteristics when relative the rotation occurs between the first and second rotary members. The second elastic member is arranged in the spring support portion and the spring accommodating aperture. The second elastic member is compressed on the positive side of the torsion characteristics when the relative rotation occurs between the first and second rotary members. However, the second elastic member is compressed on the negative side of the torsion characteristic only in a range exceeding a predetermined torsion angle. The friction generating mechanism generates a friction resistance only when the second elastic member is compressed in the rotating direction.
According to the damper mechanism of the above aspect, when the first and second rotary members rotate relatively to each other, the first and second elastic members are compressed therebetween to provide predetermined torsion characteristics. On the positive side of the torsion characteristics, the first and second elastic members are compressed to provide predetermined characteristics. Further, the friction generating mechanism generates friction in accordance with compression of the second elastic member. On the negative side of the torsion characteristics, however, only the first elastic member is compressed before the torsion angle exceeds a predetermined value. Thus, the second elastic member is not compressed, and the friction generating mechanism does not generate friction. Owing to the above operations, low rigidity characteristics can be realized on the negative side. Further, friction is not generated by the friction generating mechanism.
In summary, this damper mechanism can provide characteristics in which the predetermined rigidity and hysteresis torque are produced on the positive side or acceleration side of the torsion characteristics, and low rigidity and extremely low hysteresis torque are produced in the negative side or deceleration side of the torsion characteristics. As a result, it is possible to suppress variations in rotation speed, which may occur when passing through the resonance point, on the positive side of the torsion characteristics. Also, good damping rates can be achieved throughout the negative side of the torsion characteristics. In particular, the resonance point can be lowered to a range of small variations in engine speed because the characteristics of a low rigidity on the deceleration side can be achieved by not compressing the second elastic member. Therefore, variations in engine speed do not increase even when resonance occurs. Accordingly, it is possible to eliminate a friction generating portion that operates on the deceleration side so that the damper mechanism can have a simple mechanism. More specifically, the first and second rotary members can directly and axially contact each other, and a conventional friction generating mechanism can be eliminated from between them. The result is a damper mechanism with a simplified structure relative to conventional damper mechanism.
According to a third aspect of the present invention, the damper mechanism of the first or second aspect further has a feature such that the friction generating mechanism is arranged in the second elastic member.
According to a fourth aspect of the present invention, the damper mechanism of the third aspect further has a feature such that the second elastic member is formed of an elastic member having a high internal friction coefficient, and provides the friction generating mechanism.
According to a fifth aspect of the present invention, the damper mechanism of the third aspect further has a feature such that the second elastic member is formed of a coil spring, and the friction generating mechanism is formed of a friction generating member attached to the coil spring.
According to a sixth aspect of the present invention, the damper mechanism of the fifth aspect further has a feature such that the friction generating member is formed of an elastic member having a high internal friction coefficient and arranged in the coil spring.
According to a seventh aspect of the present invention, the damper mechanism of the fifth aspect further has a feature such that the damper mechanism further includes a guard member arranged between the elastic member and the coil spring.
These and other objects, features, aspects, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.